Therapeutic Dose Response of Acoustic Cluster Therapy in Combination With Irinotecan for the Treatment of Human Colon Cancer in Mice.

Introduction: Acoustic Cluster Therapy (ACT) comprises coadministration of a formulation containing microbubble-microdroplet clusters (PS101) together with a regular medicinal drug and local ultrasound (US) insonation of the targeted pathological tissue. PS101 is confined to the vascular compartment and when the clusters are exposed to regular diagnostic imaging US fields, the microdroplets undergo a phase shift to produce bubbles with a median diameter of 22 µm. Low frequency, low mechanical index US is then applied to drive oscillations of the deposited ACT bubbles to induce biomechanical effects that locally enhance extravasation, distribution, and uptake of the coadministered drug, significantly increasing its therapeutic efficacy. Methods: The therapeutic efficacy of ACT with irinotecan (60 mg/kg i.p.) was investigated using three treatment sessions given on day 0, 7, and 14 on subcutaneous human colorectal adenocarcinoma xenografts in mice. Treatment was performed with three back-to-back PS101+US administrations per session with PS101 doses ranging from 0.40-2.00 ml PS101/kg body weight (n = 8-15). To induce the phase shift, 45 s of US at 8 MHz at an MI of 0.30 was applied using a diagnostic US system; low frequency exposure consisted of 1 or 5 min at 500 kHz with an MI of 0.20. Results: ACT with irinotecan induced a strong, dose dependent increase in the therapeutic effect (R2 = 0.95). When compared to irinotecan alone, at the highest dose investigated, combination treatment induced a reduction in average normalized tumour volume from 14.6 (irinotecan), to 5.4 (ACT with irinotecan, p = 0.002) on day 27. Median survival increased from 34 days (irinotecan) to 54 (ACT with irinotecan, p = 0.002). Additionally, ACT with irinotecan induced an increase in the fraction of complete responders; from 7% to 26%. There was no significant difference in the therapeutic efficacy whether the low frequency US lasted 1 or 5 min. Furthermore, there was no significant difference between the enhancement observed in the efficacy of ACT with irinotecan when PS101+US was administered before or after irinotecan. An increase in early dropouts was observed at higher PS101 doses. Both mean tumour volume (on day 27) and median survival indicate that the PS101 dose response was linear in the range investigated

Ultrafast Microscopy Imaging of Acoustic Cluster Therapy Bubbles: Activation and Oscillation

Acoustic Cluster Therapy (ACT®) is a platform for improving drug delivery and has had promising pre-clinical results. A clinical trial is ongoing. ACT® is based on microclusters of microbubbles–microdroplets that, when sonicated, form a large ACT® bubble. The aim of this study was to obtain new knowledge on the dynamic formation and oscillations of ACT® bubbles by ultrafast optical imaging in a microchannel. The high-speed recordings revealed the microbubble–microdroplet fusion, and the gas in the microbubble acted as a vaporization seed for the microdroplet. Subsequently, the bubble grew by gas diffusion from the surrounding medium and became a large ACT® bubble with a diameter of 5–50 μm. A second ultrasound exposure at lower frequency caused the ACT® bubble to oscillate. The recorded oscillations were compared with simulations using the modified Rayleigh–Plesset equation. A term accounting for the physical boundary imposed by the microchannel wall was included. The recorded oscillation amplitudes were approximately 1–2 µm, hence similar to oscillations of smaller contrast agent microbubbles. These findings, together with our previously reported promising pre-clinical therapeutic results, suggest that these oscillations covering a large part of the vessel wall because of the large bubble volume can substantially improve therapeutic outcome.publishedVersio

Experimental setup for the ultrasonic fractionation of flowing whole blood in a capillary

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Lithium niobate transducers for MRI-guided ultrasonic microsurgery

Request Permissions Focused ultrasound surgery (FUS) is usually based on frequencies below 5 MHz-typically around 1 MHz. Although this allows good penetration into tissue, it limits the minimum lesion dimensions that can be achieved. In this study, we investigate devices to allow FUS at much higher frequencies, in principle, reducing the minimum lesion dimensions. Furthermore, FUS can produce deep-sub-millimeter demarcation between viable and necrosed tissue; high-frequency devices may allow this to be exploited in superficial applications which may include dermatology, ophthalmology, treatment of the vascular system, and treatment of early dysplasia in epithelial tissue. In this paper, we explain the methodology we have used to build high-frequency high-intensity transducers using Y-36°-cut lithium niobate. This material was chosen because its low losses give it the potential to allow very-highfrequency operation at harmonics of the fundamental operating frequency. A range of single-element transducers with center frequencies between 6.6 and 20.0 MHz were built and the transducers' efficiency and acoustic power output were measured. A focused 6.6-MHz transducer was built with multiple elements operating together and tested using an ultrasound phantom and MRI scans. It was shown to increase phantom temperature by 32°C in a localized area of 2.5 × 3.4 mm in the plane of the MRI scan. Ex vivo tests on poultry tissue were also performed and shown to create lesions of similar dimensions. This study, therefore, demonstrates that it is feasible to produce high-frequency transducers capable of high-resolution FUS using lithium niobate

Sonoporation at low mechanical index

International audiencehe purpose of this study was to investigate the physical mechanisms of sonoporation, in order to understand and improve ultrasound-assisted drug and gene delivery. Sonoporation is the transient permeabilisation and resealing of a cell membrane with the help of ultrasound and/or an ultrasound contrast agent, allowing for the trans-membrane delivery and cellular uptake of macromolecules between 10 kDa and 3 MDa. The authors studied the behaviour of ultrasound contrast agent microbubbles near cancer cells at low acoustic amplitudes. After administering an ultrasound contrast agent, HeLa cells were subjected to 6*6 MHz ultrasound with a mechanical index of 0*2 and observed with a high-speed camera. Microbubbles were seen to enter cells and rapidly dissolve. The quick dissolution after entering suggests that the microbubbles lose (part of) their shell while entering. The authors have demonstrated that lipid-shelled microbubbles can be forced to enter cells at a low mechanical index. Hence, if a therapeutic agent is added to the shell of the bubble or inside the bubble, ultrasound-guided delivery could be facilitated at diagnostic settings. In addition, these results may have implications for the safety regulations on the use of ultrasound contrast agents for diagnostic imaging

Acoustically active antibubbles

In this study, we analyse the behaviour of antibubbles when subjected to an ultrasonic pulse. Specically, we derive oscillating behaviour of acoustic antibubbles with a negligible outer shell, resulting in a RayleighPlesset equation of antibubble dynamics. Furthermore, we compare theoretical behaviour of antibubbles to behaviour of regular gas bubbles. We conclude that antibubbles and regular bubbles respond to an acoustic wave in a very similar manner if the antibubble's liquid core radius is less than half the antibubble radius. For larger cores, antibubbles demonstrate highly harmonic behaviour, which would make them suitable vehicles in ultrasonic imaging and ultrasound-guided drug delivery

Theranostic Attributes of Acoustic Cluster Therapy and Its Use for Enhancing the Effectiveness of Liposomal Doxorubicin Treatment of Human Triple Negative Breast Cancer in Mice.

Introduction:Acoustic cluster therapy (ACT) comprises co-administration of a formulation containing microbubble/microdroplet clusters (PS101), together with a regular medicinal drug (e.g., a chemotherapeutic) and local ultrasound (US) insonation of the targeted pathological tissue (e.g., the tumor). PS101 is confined to the vascular compartment and, when the clusters are exposed to regular diagnostic imaging US fields, the microdroplets undergo a phase-shift to produce bubbles with a median diameter of 22 µm when unconstrained by the capillary wall. In vivo these bubbles transiently lodge in the tumor's microvasculature. Low frequency ultrasound (300 kHz) at a low mechanical index (MI = 0.15) is then applied to drive oscillations of the deposited ACT bubbles to induce a range of biomechanical effects that locally enhance extravasation, distribution, and uptake of the co-administered drug, significantly increasing its therapeutic efficacy. Methods:In this study we investigated the therapeutic efficacy of ACT with liposomal doxorubicin for the treatment of triple negative breast cancer using orthotopic human tumor xenografts (MDA-MB-231-H.luc) in athymic mice (ICR-NCr-Foxn1nu). Doxil® (6 mg/kg, i.v.) was administered at days 0 and 21, each time immediately followed by three sequential ACT (20 ml/kg PS101) treatment procedures (n = 7-10). B-mode and nonlinear ultrasound images acquired during the activation phase were correlated to the therapeutic efficacy. Results:Results show that combination with ACT induces a strong increase in the therapeutic efficacy of Doxil®, with 63% of animals in complete, stable remission at end of study, vs. 10% for Doxil® alone (p < 0.02). A significant positive correlation (p < 0.004) was found between B-mode contrast enhancement during ACT activation and therapy response. These observations indicate that ACT may also be used as a theranostic agent and that ultrasound contrast enhancement during or before ACT treatment may be employed as a biomarker of therapeutic response during clinical use

Lactation-induced WAP-SV40 Tag transgene expression in C57BL/6J mice leads to mammary carcinoma.

Two transgenic lineages were generated by directing the expression of SV40 T antigen to the mammary gland of inbred C57BL/6J mice using the whey acidic protein (WAP) promoter. In one lineage, WAPTag 1, multiparous female mice developed mammary adenocarcinoma with an average latency period of 13 months. The histopathological phenotype was heterogeneous, tumours occurred in a stochastic fashion, normal tissue was located next to neoplastic tissue, the mammary tumours usually developed and were remarkably similar to that observed in human cases. In addition, male and virgin females developed a poorly differentiated SV40 T antigen-positive soft tissue sarcoma, also at 13 months of age. In the other lineage, WAPTag 3, some parous females developed mammary tumours, but most mice succumbed to osteosarcomas arising from the os petrosum at 5.5 to 6 months of age and on necropsy, renal adenocarcinomas were also found. Appearance of these unexpected tumour types demonstrates the non-specific expression of SV40 Tag under the control of the WAP promoter. The expression of SV40 Tag in mammary glands at different stages of development was also examined, and only actively lactating glands were positive. This suggests that the abundant cyclic synthesis of SV40 Tag associated with pregnancy is required for mammary tumorigenesis in these lineages

Ultrafast Microscopy Imaging of Acoustic Cluster Therapy Bubbles: Activation and Oscillation

Acoustic Cluster Therapy (ACT®) is a platform for improving drug delivery and has had promising pre-clinical results. A clinical trial is ongoing. ACT® is based on microclusters of microbubbles–microdroplets that, when sonicated, form a large ACT® bubble. The aim of this study was to obtain new knowledge on the dynamic formation and oscillations of ACT® bubbles by ultrafast optical imaging in a microchannel. The high-speed recordings revealed the microbubble–microdroplet fusion, and the gas in the microbubble acted as a vaporization seed for the microdroplet. Subsequently, the bubble grew by gas diffusion from the surrounding medium and became a large ACT® bubble with a diameter of 5–50 μm. A second ultrasound exposure at lower frequency caused the ACT® bubble to oscillate. The recorded oscillations were compared with simulations using the modified Rayleigh–Plesset equation. A term accounting for the physical boundary imposed by the microchannel wall was included. The recorded oscillation amplitudes were approximately 1–2 µm, hence similar to oscillations of smaller contrast agent microbubbles. These findings, together with our previously reported promising pre-clinical therapeutic results, suggest that these oscillations covering a large part of the vessel wall because of the large bubble volume can substantially improve therapeutic outcome